An absorbent product which possesses two longitudinal side edges, two transverse end edges, a longitudinal centre line and a transverse centre line, and which comprises a liquid-permeable outer layer, a liquid-impermeable backing layer and an absorption core which is located between the said outer layer and the said backing layer, with the said absorption core comprising a first and a second absorption layer, with the first absorption layer being arranged behind the liquid-permeable outer layer and the second absorptive layer being arranged between the first absorption layer and the liquid-impermeable backing layer, with the first absorption layer having two longitudinal channels, with each of the channels having an outer edge closest to the corresponding longitudinal side edge of the product and an inner edge closest to the longitudinal centre line of the product.
A problem with absorbent products is that of ensuring that they do not leak. Leakage is not usually due to the total absorptive capacity of the product being insufficient. Instead, the reason for the leakage can, for example, be that released liquid ends up outside the absorption body due to the product having come to be located in an incorrect position when being put on or as a consequence of stresses during use, or that the product has been deformed such that the surface available for liquid absorption has become insufficient. Another common reason for leakage is that the liquid runs along the surface of the product without being absorbed due to the product exhibiting low instantaneous liquid absorption or having been deformed in an undesirable manner when being used.
It has been previously known, from U.S. Pat. No. 4,655,759, to provide an absorbent product with compressed, arcuated channels which are arranged in the longitudinal direction of the absorption core. The compressed channels are stated to assist the article in forming the shape of a W in cross-sectional profile when the article is pressed together by the thighs of the user. The improved fit is said to minimize the risk of leakage. Beyond the compressed channels, in the direction towards the rearside, i.e. in that part of the product which is arranged, during use, closest to the back and the caudal vertebra, the cross-sectional profile is changed to an inverted V shape. This is said to make it possible to achieve a better fit between the buttocks of the user.
WO 95/15139 attempts to solve the problem of lateral leakage by means of compressed channels which shape the absorbent article into a container for the liquid when the article is used. In addition, the channels help the article to distance itself somewhat from the user. WO 90/14814 uses sewn or glued channels in order to obtain an effect of upturned edges which is said to protect against lateral leakage. EP 0,249,405 uses compressed, arcuate longitudinal channels on each side of an elevation on the core. In addition, the channels can extend further to compressed areas or be arranged around the whole of the core. This is stated to ensure that full contact is achieved between the user and the article and to prevent lateral leakage.
However, the abovementioned inventions fail to identify and indicate a satisfactory way in which all possibilities of leakage can be avoided.
An aim of the present invention is to improve existing efforts to solve the above problem. Another aim of the present invention is to improve instantaneous liquid absorption at the same time as obtaining a good, stable and user-friendly fit and thereby to decrease discomfort, leakage and skin irritations which can arise due to the product chafing the skin.
The present invention has been used to achieve an absorbent product of the type mentioned at the outset, which product essentially eliminates the problems associated with previously known products of this nature.
The product which is designed in accordance with the invention is principally distinguished by the fact that the two longitudinal channels extend through the whole of the thickness of the first absorptive layer and that a compressed area is arranged between the longitudinal sides of the absorbent product and that the distance between the side edges of the compressed area is smaller than or equal to the distance between the outer side edges of the longitudinal channels.
The combination of the longitudinal channels and the compressed area between the channels results in high instantaneous liquid absorption, with a good fit at the same time being retained during the dry state. The liquid which the product receives can penetrate rapidly and readily down through the channels to the underlying core, resulting in more rapid admission. The channels also shape the product in conformance with the inside of the user""s thighs, resulting in a good U-like fit being achieved. A good fit minimizes leakage which can occur due to occasional gaps which are formed between the absorbent product and the user""s body. The compressed area contributes to ensuring a good fit and increases the stability and deformation resistance of the product, thereby helping the absorbent product to remain in place during use. In addition, the second absorptive layer serves to hide the channels so that the latter cannot be seen through the liquid-impermeable backing layer, something which might otherwise be regarded by users as being disturbing and disquieting. A particularly good masking effect is obtained if the compressed area is arranged in the second absorptive layer. A further advantage of the invention is also the fact that substantial economies in material can be obtained due to it being possible to recirculate all the material which has been removed from the channels back to earlier production stages.
The compressed area preferably extends transversely the whole way between the outer edges of the two channels. In addition, the longitudinal extent of the compressed area preferably corresponds essentially to the length of the channels. Alternatively, the length of the compressed area can be greater or less than the length of the channels; for example, the compressed area can extend the whole length of the absorptive body. It is also possible to design the compressed area with straight side edges even if the channels have a curved shape, or vice versa. Moreover, if the compressed area extends past the ends of the channels, the portion or portions of the compressed area being located beyond the channels may have a greater width than the distance between the outer edges of the channels. This situation can occur, for instance, when the channels are curved and the compressed area has curved longitudinal edges which follows the contour of the channels and extend in a curved fashion beyond the ends of the channels. However, preference is given to designing the side edges of the compressed area such that they the have the same general shape as the channels.
According to an alternative embodiment, it is possible to arrange a further two longitudinal arcuate channels in the second absorption layer, with the channels extending through the whole of the thickness of the second absorption layer. The masking effect of the second absorption layer is naturally lost in such an embodiment.
According to one embodiment, the first absorption layer consists of chemical thermomechanical pulp and the second absorption layer consists chemical pulp. Chemical thermomechanical pulp will henceforth be termed CTMP and chemical pulp will henceforth be termed CP. A CTMP layer has a relatively open structure with relatively large capillaries since CTMP fibres are rigid and moderately coarse. To a large extent, the open structure remains even after wetting since the fibres retain much of their rigidity. Consequently, an absorption layer composed of CTMP has a comparatively great ability to take up liquid instantaneously and good ability to retain liquid but a comparatively poor ability to spread liquid.
CP fibres are thin and flexible and form a fibre structure having relatively small capillaries when they are laid in a layer. An absorption layer composed of CP fibres has a great ability to spread liquid; however, because the capillaries are small, absorption into the layer only takes place slowly. It is obviously possible, within the scope of the invention, to conceive of the first absorption layer consisting of CP and the second absorption layer consisting of CTMP.
Different types of absorbent foam, and absorbent bound or unbound fibre structures, consisting entirely or partly of absorbent fibres such as cotton, rayon, peat, flax or the like, are other absorptive materials which can be used when constructing an absorbent product according to the invention. It is furthermore possible for the absorbent product to comprise so-called super absorbents, which are absorbent polymeric materials which are able to absorb many times their own weight of body liquid, thereby forming an aqueous gel. Superabsorbents exist in the form of particles, fibres, flakes, granules or films and can be mixed with other materials in the absorption body or be arranged in separate layers.
According to one embodiment, the first absorption layer is smaller in the longitudinal direction than the second absorption layer. The first absorption layer can also be smaller in the transverse direction than the second absorption layer. This enables the absorption capacity to be optimized to the wetting region, i.e. that part of the product which is expected to be the first to be wetted by liquid.
It is naturally also possible, within the scope of the invention, to conceive of a structure in which the first absorption layer is larger in the longitudinal direction than the second absorptive layer. The first absorption layer can also be larger in the transverse direction than the second absorption layer.
According to another embodiment, the first absorption layer is compressed between the outer edges of the two longitudinal channels, i.e. the edges closest to the longitudinal side edges of the product. A compression in a part of the first absorption layer stabilizes the absorbent product in the dry state. In addition, the total thickness of the absorbent product is reduced and, as a result, the product is not felt to be as uncomfortable as would otherwise be the case.
According to yet another embodiment, the second absorption layer is compressed and the width of the compressed area is smaller than or equal to the distance between the outer edges of the two longitudinal channels. A compression in a part of the second absorption layer, like compression of the first absorption layer, stabilizes the shape in the dry state. It also contributes to the channels not being visible through the liquid-impermeable backing layer, something which can otherwise be regarded by the user as being disturbing and disquieting. Together with the pulp recesses in the first absorption layer, the compressed region creates folding directions for a bowl shape in the crotch part of the product, resulting in the product having a U-like shape during use. It is also possible, within the scope of the invention, to arrange for the compressed area to consist of a separate layer whose transverse extent is smaller than or equal to the distance between the outer edges of the longitudinal channels.
The density of the area of the compressed absorption layer can be 0.1-0.5 g/cm3, preferably 0.14-0.5 g/cm3, and most preferably 0.18-0.3 g/cm3.
According to one embodiment, the first absorption layer contains superabsorbents. The presence of superabsorbents in the first absorption layer provides compensation for the absorptive ability which is lost due to absorptive material being removed when the channels are made. Taken together with the channels, they result in a product exhibiting very high instantaneous liquid absorption.
According to one embodiment, the second absorption layer contains superabsorbents. The presence of superabsorbents in the second absorption layer results in the absorbent product being able to absorb and store large quantities of liquid.
It is naturally also possible, within the scope of the invention, to conceive of a structure in which both the first and the second absorption layers contain superabsorbent. It is also possible, within the scope of the invention, to conceive of a product which contains two or more different types of superabsorbent in the first and/or second absorption layers.
According to one embodiment, the longitudinal channels are arcuate. Arcuate channels contribute to further improving the fit when the product is used. Thus, the channels provide a comfortable and superior fit in addition to permitting high instantaneous liquid absorption. The channels constrain the product to assume a U-like shape when the product is used.
The length of each longitudinal channel is preferably 10-22 cm. This does not rule out the length of the channels being matched to the size of the absorbent product or, for that matter, to the size of the first absorption layer. The distance between the inner edges of each longitudinal channel can vary in the longitudinal direction of the product and is 1.0-9.0 cm, preferably 1.0-7.0 cm, or most preferably 2.0-4.5 cm. It is also possible, within the scope of the invention, to conceive of a structure in which the distance between the inner edges of each longitudinal channel is constant in the longitudinal direction of the product. Naturally, such a channel structure would give rise to arcuate channels. The width of the longitudinal channels is 0.1-1.0 cm.
According to one embodiment, the first absorption layer is 22-25 cm in the longitudinal direction and the second absorption layer is 30-33 cm in the longitudinal direction.
Furthermore, the absorbent product according to the invention can contain at least one odour-inhibiting substrate in the first absorption layer. The second absorption layer can also contain at least one odour-inhibiting substrate. Examples of some of the odour-inhibiting substrates which can be used are zeolites, active charcoal, ion exchangers, different forms of pH-regulating substances, for example acids or partially neutralized superabsorbents, etc.
According to one embodiment, the length of the compressed area is 13-22 cm, preferably 16-20 cm, and most preferably 17-18 cm. The distance between the side edges of the compressed area is 1-8 cm, preferably 3-6.5 cm, and most preferably 4-5.5 cm.